Mains Electricty in the UK is supplied at 230 volts / 50 Hertz (compare world standards HERE or HERE).
It used to be set at 240 volts, but the EU decided it should be turned down a notch so people don’t fatally electrocute themselves quite as badly if they do something stupid (elf & safety / health & safety)
Electrical Plugs & Sockets conform to BS1363 standards, which is regarded as the best and safest in the world (or at least one of them).
DIY jobs you can do on the electrical system in your home these days are limited by the Part P Regulations brought in by the Labour Government of Tony Blair a number of years ago on the grounds of health & safety. Most electricians will tell you it is more of a money making exercise.